Hi,
my english only google translate, sorry
1. Works on a clean install Seblod
2. After 3->4 update I had this problem - item not fixed in the right place when dragging
3.This helped me:
3.1 In list settings (List -> Template) there is a parameter: data-draggable-group="$cck->getValue('art_catid')"
3.2. So on the page there should be a field 'art_catid'
4.now works
Also carefully compare the settings of a clean installation and your site.
best regards